A broad diversity of devices is known for diffusing fragrances or air-freshening substances, as well as for insecticides, both active (for example, electrical) and passive. The active devices usually have a heater element which heats a solid or liquid material which includes the volatile substance it is desired to diffuse, to evaporate it. The passive devices (or non-electrical) are usually based on the spontaneous evaporation of the volatile substance, for example, by means of evaporation of the same at room temperature.
U.S. Pat. No. 4,739,928 and U.S. Pat. No. 4,621,768 describe passive air-freshening devices of the type of those which incorporate a wick in contact with the air-freshening liquid, which have means to regulate the evaporation of the liquid. U.S. Pat. No. 4,739,928 describes how the adjustment of the emanation of fragrance is achieved through an emanator or absorbent cap coupled to the neck of the container which conforms the air-freshener, by means of a rotational movement of a cover which covers a holder wherein said absorbent cap is housed. U.S. Pat. No. 4,621,768 describes how the regulation of the evaporation of a liquid is achieved by means of some slits arranged in a cover which also rotates, to vary the fragrance-diffusing surface without altering the original form of the apparatus in itself.
U.S. Pat. No. 5,725,152 describes another air-freshener dispenser, which can be used for a long time because the emanator medium is easily replaceable, without prejudice to deforming the air-freshener, to which a special ornamental appearance is given with a cover in the form of a flower.
U.S. Pat. No. 4,928,881 describes a device which contains air-freshening liquid and wick, it being possible to separate the wick and the container of the liquid with respect to the base of the air-freshener which, for its peculiar form can be used for other purposes, such as an ashtray or flowerpot holder, etc.
WO-A-2004/110559 (corresponding to the international patent application no. PCT/ES03/00291) describes an air-freshening device based on the adjustable evaporation of a liquid and which has a cap, to which are incorporated means which prevent it being dismounted from a plug which, on being rotated without the possibility of being extracted from the device, opens the apertures which are present in the plug, exposing a wick impregnated in liquid to the air.
The German patent DE-676131 reflects another system of passive evaporation, based on drops falling from a raised recipient, over evaporation surfaces. The liquid can be collected in a recipient underneath.
ES-U-1013798 describes an air-freshening device in which the substance to evaporate is inside a casing with a generally spherical form which comprises two parts that can be rotated around each other, so that it is possible to vary the size of some orifices or apertures which allow the evaporated substance to pass from the interior of the casing to the exterior.
GB-A-2371750 describes a transparent air-freshening device based on the use of liquids selected so that a change of colour or the like takes place when the active substance to be evaporated has been exhausted.
U.S. Pat. No. 2,412,128 describes a device that can evaporate an active substance when it is positioned “downwards”.
EP-A-1088561 describes a number of devices for diffusing volatile substances based on the use of a special wick which acts so that the liquid to evaporate can only be absorbed from a point near to the bottom of the container or reservoir which holds the liquid. Thus, if the reservoir is positioned “downwards”, no evaporation of the liquid takes place. This allows configurations to be implemented with several containers or reservoirs which can hold different volatile active substances, and wherein the substance to evaporate is chosen by positioning the corresponding container “upwards”.
U.S. Pat. No. 4,889,286 describes an air-freshener in which a vessel, which holds a liquid which contains the volatile substance it is desired to diffuse, can be located selectively “upwards” or “downwards”, the vessel having a cap with vent holes covered by a membrane of a material with micropores. Thus, when the container is upright, the liquid is not in contact with the membrane, and the membrane serves as a barrier to prevent the volatile substances (present inside the container) from discharging to the exterior. When the container is inverted, the liquid rests on the membrane and impregnates the pores or micropores, whereby the volatile substances can pass into the atmosphere. Thus, it can be said that the device is in the active or ON state when the container is located with its face downward, and in a non-active or OFF state when the container is with its face upward.
As for the active evaporation devices, a great number of the same is to be found which describe systems based on an electric heater element. ES-U-1049393 describes a system of this type which includes a box in which several electric evaporators are located. The system is configured so that it is possible to program selective connection and disconnection of the evaporators and thereby achieve an overall evaporation intensity, uniform in time.